Figure 5. Suspended lath ceiling.
e. Lead-lined blocks. Lead-lined blocks, also called leadcore blocks, consist of an unpierced sheet of lead bonded
in the center of a block of lightweight aggregate and concrete. Block sizes will be 12 by 12 by 4 inches for lead thickness
less than 6.0 millimeters, and 12 by 12 by 6 inches for lead thickness over 6.0 millimeters, with enough half-blocks for
proper bonding of the wall. The blocks are an interlocking lock-joint and self-aligning type. Blocks designed to have lead
laps at joints are erected in a manner that provides a minimum 1 inch tight lap without soldering or burning. Heavy lead-
lined blocks, with a lead thickness from 9.0 millimeters to 20.0 millimeters, or heavier are used for high-energy radiation
shielding. The heavy lead-lined blocks are designed to receive a lead bar, of the same thickness of lead used in blocks,
horizontally and vertically at all joints to provide an effective lead lap with adjoining blocks. See figures 6 and 7 for details.
(1) Where the floor is lead-lined, the first course of blocks is laid on lead strips at least 7 inches wide and will
project at least 3 inches inside the partition. Starter blocks are required when the sheet lead that is cast in the center of
the block is over 6.0 millimeters thick. Lead-lined blocks are installed in courses with staggered vertical joints. A
maximum 1/2-inch mortar joint is allowed. Mortar between lead laps is not permitted.
(2) The lead-lined blocks with a lead thickness less than 9.0 millimeters will have rabbetted edges formed by
off-setting slabs on opposite sides of the lead. The lead is exposed on all sides to provide a 1-inch lap at all joints when